/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.naming.factory;

import javax.mail.Authenticator;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.naming.Context;
import javax.naming.Name;
import javax.naming.RefAddr;
import javax.naming.Reference;
import javax.naming.spi.ObjectFactory;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Properties;

/**
 * <p>Factory class that creates a JNDI named JavaMail Session factory,
 * which can be used for managing inbound and outbound electronic mail
 * messages via JavaMail APIs.  All messaging environment properties
 * described in the JavaMail Specification may be passed to the Session
 * factory; however the following properties are the most commonly used:</p>
 * <ul>
 * <li>
 * <li><strong>mail.smtp.host</strong> - Hostname for outbound transport
 * connections.  Defaults to <code>localhost</code> if not specified.</li>
 * </ul>
 * <p>
 * <p>This factory can be configured in a
 * <code>&lt;Context&gt;</code> element in your <code>conf/server.xml</code>
 * configuration file.  An example of factory configuration is:</p>
 * <pre>
 * &lt;Resource name="mail/smtp" auth="CONTAINER"
 *           type="javax.mail.Session"/&gt;
 * &lt;ResourceParams name="mail/smtp"&gt;
 *   &lt;parameter&gt;
 *     &lt;name&gt;factory&lt;/name&gt;
 *     &lt;value&gt;org.apache.naming.factory.MailSessionFactory&lt;/value&gt;
 *   &lt;/parameter&gt;
 *   &lt;parameter&gt;
 *     &lt;name&gt;mail.smtp.host&lt;/name&gt;
 *     &lt;value&gt;mail.mycompany.com&lt;/value&gt;
 *   &lt;/parameter&gt;
 * &lt;/ResourceParams&gt;
 * </pre>
 *
 * @author Craig R. McClanahan
 */
public class MailSessionFactory implements ObjectFactory {

	/**
	 * The Java type for which this factory knows how to create objects.
	 */
	protected static final String factoryType = "javax.mail.Session";

	/**
	 * Create and return an object instance based on the specified
	 * characteristics.
	 *
	 * @param refObj  Reference information containing our parameters, or null
	 *                if there are no parameters
	 * @param name    The name of this object, relative to context, or null
	 *                if there is no name
	 * @param context The context to which name is relative, or null if name
	 *                is relative to the default initial context
	 * @param env     Environment variables, or null if there are none
	 * @throws Exception if an error occurs during object creation
	 */
	@Override
	public Object getObjectInstance(Object refObj, Name name, Context context,
	                                Hashtable<?, ?> env) throws Exception {

		// Return null if we cannot create an object of the requested type
		final Reference ref = (Reference) refObj;
		if (!ref.getClassName().equals(factoryType))
			return (null);

		// Create a new Session inside a doPrivileged block, so that JavaMail
		// can read its default properties without throwing Security
		// exceptions.
		//
		// Bugzilla 31288, 33077: add support for authentication.
		return AccessController.doPrivileged(new PrivilegedAction<Session>() {
			@Override
			public Session run() {

				// Create the JavaMail properties we will use
				Properties props = new Properties();
				props.put("mail.transport.protocol", "smtp");
				props.put("mail.smtp.host", "localhost");

				String password = null;

				Enumeration<RefAddr> attrs = ref.getAll();
				while (attrs.hasMoreElements()) {
					RefAddr attr = attrs.nextElement();
					if ("factory".equals(attr.getType())) {
						continue;
					}

					if ("password".equals(attr.getType())) {
						password = (String) attr.getContent();
						continue;
					}

					props.put(attr.getType(), attr.getContent());
				}

				Authenticator auth = null;
				if (password != null) {
					String user = props.getProperty("mail.smtp.user");
					if (user == null) {
						user = props.getProperty("mail.user");
					}

					if (user != null) {
						final PasswordAuthentication pa = new PasswordAuthentication(user, password);
						auth = new Authenticator() {
							@Override
							protected PasswordAuthentication getPasswordAuthentication() {
								return pa;
							}
						};
					}
				}

				// Create and return the new Session object
				Session session = Session.getInstance(props, auth);
				return (session);

			}
		});
	}
}
